Laminate LC filter having combined condenser and coil functions

ABSTRACT

An LC filter is provided which includes a first conductive sheet, a first dielectric sheet laminated on the first conductive sheet, a second conductive sheet laminated on the first dielectric sheet, a second dielectric sheet laminated on the second conductive sheet, a third conductive sheet laminated on the second dielectric sheet, and a third dielectric sheet laminated on a third conductive sheet formed as an integral body which has the first, the second and the third conductive sheets and the first, the second and the third dielectric sheets, are coiled. The first and the second conductive sheets are respectively provided with input terminals and output terminals.

This is a division of application Ser. No. 07/824,605 (now U.S. Pat. No.5,227,746), filed on Jan. 23, 1992.

The present invention relates to an LC filter which is a composite partcombining condenser and coil functions.

FIGS. 101, 102 and 103 show a conventional noise filter which isdisclosed, for instance, in Japanese Unexamined Patent Publication No.316013/1989. FIG. 101 is an exploded view of film sheets, FIG. 102, aperspective view showing a state in which the film sheets are laminatedand coiled, and FIG. 103, an equivalent circuit diagram.

In FIGS. 101, 102 and 103, reference numerals 20a and 21a designatefirst terminals, 41a and 41b, second terminals, and 22a and 23a, thirdterminals. Reference numerals 43, 1a, 47a, 47b and 2a designateconductive foils, and 4, 45a and 45b, film sheets. In FIG. 102, areference numeral 19 designates a coil, and 17, a core insertion hole.In FIG. 103, reference numerals 10, 11 and 12 designate condensers, 7and 8, inductances. In FIG. 101, the conductive foil 1a is laminated onthe film sheet 4, and the terminal 20a and the other terminal 21a arefixed on the conductive foil 1a, respectively, by the conductive foils43, by which a first electrode is composed. The conductive foils 47a and47b are laminated on the film sheets 45a and 45b, respectively, and theother terminal 41a is fixed on the conductive foil 47a by the conductivefoil 43, by which a second electrode is composed. The other terminal 41bis fixed on the conductive foil 47b by the conductive foil 43, by whicha third electrode is composed. The conductive foil 2a is laminated onthe film sheet 4, and the terminal 22a and the other terminal 23a arefixed on the conductive foil 2a, by the conductive foils 43, by which afourth electrode is composed. Next, the second electrode and the thirdelectrode are laminated on both ends of the fourth electrode, on whichthe first electrode is laminated. As shown in FIG. 102, the film sheetsand the conductive foils which are respectively connected to the firstelectrodes, the second electrodes, the third electrodes and the fourthelectrodes, are laminated and coiled around the core insertion hole 17.

This noise filter having the above construction in which single bodiesof coil and condenser parts are not combined, and in which the filmsheets and the conductive foils are simultaneously coiled, can have afunction combining a coil and a condenser. Accordingly, in theequivalent circuit of FIG. 103 the inductance 7 is formed by winding upthe conductive foil 1a, and similarly the inductance 8 is formed by theconductive foil 2a. The condenser 10 is formed by the conductive foils47a and 47b, the conductive foil 1a and the film sheet 4, and similarlythe condenser 11 is formed by the conductive foils 47a and 47b, theconductive foil 2a, and the film sheets 45a and 45b. Furthermore, thecondenser 12 is formed by the conductive foil 1a, the film sheet 4, andthe conductive foil 2a.

Since the conventional filter is composed as above, a distributedcapacity is generated among the layers of the coiled conductive foils,which causes deterioration of high-frequency characteristic of theinductance, and deterioration of the filter characteristic. Since thefilter is produced by coiling a plurality of laminated conductive foilsand film sheets, the production of the filter is difficult. Furthermore,automation of the production process is difficult since the processrequires a step for taking out the terminals. Furthermore, since thesetting of the respective constants of the inductance and the condenserwhich determine the filter characteristic, is mainly performed byselecting a coiled length of the conductive foils and the film sheets,the control of the setting is difficult.

It is an object of the present invention to provide an LC filter capableof solving the above problems, by which an LC filter is obtained whichis improved in its high-frequency characteristic, and an LC filter isobtained in which the method of the production is comparatively simple,and an LC filter is obtained in which the automation of productionbecomes possible, and the filter characteristic can easily be set.

According to an aspect of the present invention, there is provided an LCfilter which comprises:

a first conductive sheet; a first dielectric sheet laminated on thefirst conductive sheet; a second conductive sheet laminated on the firstdielectric sheet; a second dielectric sheet laminated on the secondconductive sheet; a third conductive sheet laminated on the seconddielectric sheet; and a third dielectric sheet laminated on a thirdconductive sheet;

wherein an integral body consisting of the first, the second and thethird conductive sheets and the first, the second and the thirddielectric sheets, is coiled; and

the first and the second conductive sheets are respectively providedwith input terminals and output terminals and the third conductive sheetis provided with another terminal for connection to ground.

According to another aspect of the present invention, there is provideda unit LC filter for laminating which comprises:

a first and a second conductive sheet each having a ring-like shape ofwhich a portion is cut off from an inner opening thereof to an outerperiphery thereof; and

a dielectric film interposed between the first and the second conductivesheets;

wherein the first and the second conductive sheets are respectivelyprovided with input terminals and output terminals.

According to another aspect of the present invention, there is provideda unit LC filter for laminating of the above aspect, wherein the inputterminals and the output terminals are respectively provided at each ofedges of the cut-off portions of the first and the second conductivesheets and on radial lines passing through centers of the first and thesecond conductive sheets.

According to another aspect of the present invention, there is provideda unit LC filter for laminating which comprises:

a first laminated body wherein a plurality of ring-like conductivesheets and a plurality of dielectric sheets a portion of each of whichis cut off from an inner opening thereof to an outer periphery thereofare alternatively laminated shifting the cut-off portions of theconductive sheets and the dielectric sheets; and

a second laminated body composed in the same way as in the firstlaminated body;

wherein first ends of the cut-off portions of the first laminated bodyare laminated and connected to second ends of the cut-off portions ofthe second laminated body.

According to another aspect of the present invention, there is provideda unit LC filter for laminating which comprises:

a first and a second conductive sheet a portion of each of which is cutoff from an inner opening thereof to an outer periphery thereof; and

a magnetic sheet interposed between the first and the second conductivesheets;

wherein the first and the second conductive sheets are provided withinput terminals and output terminals, respectively.

Furthermore, as shown in the embodiments (mentioned later), thefollowing laminating means may be provided for multi-layer type LCfilters.

A multi-layer filter is provided wherein unit layer LC filters arelaminated in multiple layers interposing dielectric films, andconnection terminals provided at edges of the cut-off portions of thefirst and second conductive sheets are successively connected, by whichthe respective conductive sheets are connected forming a coil-likeconnection.

A multi-layer LC filter is provided, wherein the unit layer LC filterseach provided with a third conductive sheet interposing a dielectricfilm, are laminated in multiple layers interposing dielectric films, andconnection terminals provided at edges of the cut-off portions of thefirst and the second conductive sheets are successively connected, bywhich the respective conductive sheets are connected forming a coil, andthe third conductive sheets are connected to each other.

A multi-layer LC filter is proposed in which a laminated body whereinmagnetic sheets are inserted among the first, the second and the thirdconductive sheets, and the integral body is laminated interposingmagnetic sheets, and another laminated body wherein magnetic sheets anddielectric films are interposed among the first, the second and thethird conductive sheets, are laminated interposing magnetic sheets anddielectric films.

A multi-layer filter is proposed in which a multi-layer filter whereinunit layer LC filters composed of the first and second conductive sheetsand dielectric films interposed therebetween, are laminated in arbitrarynumber, and another multi-layer filter wherein a third conductive sheetis laminated on the above unit layer LC filter interposing a dielectricfilm, are laminated in arbitrary number interposing dielectric films,and both multi-layer filters are laminated.

Furthermore, a plurality of conductive sheets are provided each havingan opening at a central portion thereof, a cut-off portion provided fromthe opening to a periphery thereof and terminals at the cut-offportions, and a plurality of dielectric films are provided each having aprotrusion or a recess or a hole for connecting top and bottomconductive sheets and also for positioning. The connecting terminalprovided at one cut-off edge of a conductive sheet communicates with theother terminal of the other cut-off edge of another conductive sheet bycontact thereto or by a conductive adhesive agent. Filters wherein twopairs of the connected conductive sheets are alternatively laminated,and the dielectric sheets are inserted between the conductive sheets,are laminated in a single step or in multi-steps, and connected inseries from the first layer to the Nth layer, by contact or by aconductive adhesive agent.

Furthermore, the LC filter is composed of two-face-substrates, wherein apattern thickness of the bottom surface of the two-face-substrate islarger than that of the top surface by the thickness of the dielectricfilm, and the substrates are laminated in a single step or inmulti-steps, and are connected in series from the first to the Nthlayers.

Furthermore, an LC filter is composed by connecting the first filterwherein filters in which the conductive sheets are connected inparallel, are laminated in a single step or in multi-steps from thefirst to the Nth layer, in parallel, the second filter wherein the otherconductive sheets are provided between the respective layers of the LCfilter, mentioned above and the other conductive sheets are grounded,and the LC filter, mentioned above, are connected in series, andequipped with a core, if necessary.

In the drawings:

FIG. 1 is an exploded view of an embodiment 1 according to the presentinvention;

FIG. 2 is a diagram showing a layer construction of the embodiment 1according to the present invention;

FIG. 3 is an equivalent circuit diagram of the embodiment 1 according tothe present invention;

FIG. 4 is a perspective view of the embodiment 1 according to thepresent invention;

FIG. 5 is a diagram showing an impedance characteristic of theembodiment 1 according to the present invention;

FIG. 6 is a plan showing a conductive sheet of an embodiment 3 accordingto the present invention;

FIG. 7 is a front view of the conductive sheet of the embodiment 3according to the present invention;

FIG. 8 is a plan of a unit layer LC filter of the embodiment 3 accordingto the present invention;

FIG. 9 is a front view of the unit layer LC filter of the embodiment 3according to the present invention;

FIG. 10 is an equivalent circuit diagram of the unit layer LC filter ofthe embodiment 3 according to the present invention;

FIG. 11 is a plan showing a multi-layer LC filter of the embodiment 3according to the present invention;

FIG. 12 is a front view of the multi-layer LC filter of the embodiment 3according to the present invention;

FIG. 13 is an equivalent circuit diagram of the multi-layer LC filter ofthe embodiment 3 according to the present invention;

FIG. 14 is a perspective view of the multi-layer LC filter of theembodiment 3 according to the present invention;

FIG. 15 is a front view of a multi-layer LC filter of an embodiment 4according to the present invention;

FIG. 16 is an equivalent circuit diagram of the multi-layer LC filter ofthe embodiment 4 according to the present invention;

FIG. 17 is a plan showing a laminated body composed of a conductivesheet and a dielectric film of an embodiment 6 according to the presentinvention;

FIG. 18 is a plan of a unit layer LC filter of an embodiment 8 accordingto the present invention;

FIG. 19 is a front view of the unit layer LC filter of the embodiment 8according to the present invention;

FIG. 20 is a diagram showing a connection of the unit layer LC filtersof the embodiment 8 according to the present invention;

FIG. 21 is a front view of a multi-layer LC filter of an embodiment 9according to the present invention;

FIG. 22 is an equivalent circuit diagram of the multi-layer LC filter ofthe embodiment 9 according to the present invention;

FIG. 23 is a plan of a conductive sheet of an embodiment 11 according tothe present invention;

FIG. 24 is a plan of a dielectric film of the embodiment 11 according tothe present invention;

FIG. 25 is a sectional diagram wherein the conductive sheet and thedielectric film of the embodiment 11 are laminated according to thepresent invention;

FIG. 26 is a plan of another dielectric sheet of the embodiment 11according to the present invention;

FIG. 27 is a plan of another dielectric film of the embodiment 11according to the present invention;

FIG. 28 is a sectional diagram wherein the conductive sheet and thedielectric film of the embodiment 11 are laminated according to thepresent invention;

FIG. 29 is a plan of another conductive sheet of the embodiment 11according to the present invention;

FIG. 30 is a plan of another dielectric film of the embodiment 11according to the present invention;

FIG. 31 is a sectional diagram wherein the conductive sheet and thedielectric film of the embodiment 11 are laminated according to thepresent invention;

FIG. 32 is a plan of another conductive sheet of the embodiment 11according to the present invention;

FIG. 33 is a plan of another dielectric film of the embodiment 11according to the present invention;

FIG. 34 is a sectional diagram wherein the conductive sheet and thedielectric film of the embodiment 11 are laminated according to thepresent invention;

FIG. 35 is a connection diagram of the conductive sheets of theembodiment 11 according to the present invention;

FIG. 36 is an equivalent circuit diagram of the embodiment 11 accordingto the present invention;

FIG. 37 is a top view showing a two-face-substrate of an embodiment 12according to the present invention;

FIG. 38 is a bottom view showing the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 39 is a sectional diagram of the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 40 is a top view showing another two-face-substrate of theembodiment 12 according to the present invention;

FIG. 41 is a bottom view showing the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 42 is a sectional diagram of the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 43 is a top view showing another two-face-substrate of theembodiment 12 according to the present invention;

FIG. 44 is a bottom view showing the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 45 is a sectional diagram of the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 46 is a top view showing another two-face-substrate of theembodiment 12 according to the present invention;

FIG. 47 is a bottom view showing the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 48 is a sectional diagram showing the two-face-substrate of theembodiment 12 according to the present invention;

FIG. 49 is an exploded diagram of a multi-layer substrate of anembodiment 13 according to the present invention;

FIG. 50 is a top view showing a two-face-substrate of an embodiment 14according to the present invention;

FIG. 51 is a bottom view showing the two-face-substrate of theembodiment 14 according to the present invention;

FIG. 52 is a sectional diagram of the two-face-substrate of theembodiment 14 according to the present invention;

FIG. 53 is a top view showing another two-face-substrate of theembodiment 14 according to the present invention;

FIG. 54 is a bottom view showing the two-face-substrate of theembodiment 14 according to the present invention;

FIG. 55 is a sectional diagram of the two-face-substrate of theembodiment 14 according to the present invention;

FIG. 56 is a connection diagram of conductive sheets of the embodiment14 according to the present invention;

FIG. 57 is an equivalent circuit diagram of the embodiment 14 accordingto the present invention;

FIG. 58 is a top view showing a two-face-substrate of an embodiment 15according to the present invention;

FIG. 59 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 60 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 61 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 62 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 63 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 64 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 65 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 66 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 67 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 68 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 69 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 70 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 71 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 72 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 73 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 74 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 75 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 76 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 77 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 78 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 79 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 80 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 81 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 82 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 83 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 84 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 85 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 86 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 87 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 88 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 89 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 90 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 91 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 92 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 93 is a top view showing another two-face-substrate of theembodiment 15 according to the present invention;

FIG. 94 is a bottom view showing the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 95 is a sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 96 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 97 is another sectional diagram of the two-face-substrate of theembodiment 15 according to the present invention;

FIG. 98 is a connection diagram of conductive sheets of the embodiment15 according to the present invention;

FIG. 99 is an equivalent circuit of the embodiment 15 according to thepresent invention;

FIG. 100 is another equivalent circuit of the embodiment 15 according tothe present invention;

FIG. 101 is an exploded view of a conventional noise filter;

FIG. 102 is a perspective view of the conventional noise filter; and

FIG. 103 is an equivalent circuit diagram of the conventional noisefilter.

EMBODIMENT 1

FIGS. 1, 2, 3 and 4 are an exploded view, a diagram showing a layerconstruction, an equivalent circuit diagram and a perspective viewshowing appearance of an embodiment of this invention, respectively. InFIG. 1, notations 1a, 2a and 3a designate respectively a first, a secondand a third conductive foil, and 4, a dielectric film. A numeral 19designates a coil formed by coiling the above elements. Notations 20a,21a, 22a, 23a and 25a respectively designate terminals.

The coil 19 is formed in the following way. The dielectric film 4 islaminated on the conductive foil 3a having the terminals 25a, on whichthe conductive foil 2a having the terminals 22a and 23a, the dielectricfilm 4, the conductive foil 1a having the terminals 20a and 21a, and thedielectric film 4, are successively laminated. The laminated body iscoiled, by which the coil 19 is obtained.

FIG. 2 is a diagram showing a layer construction of the coil 19 in whichthe conductive foils 1a, 2a and 3a, and the dielectric films 4 arecoiled. In FIG. 2, a numeral 9 designates a distributed capacitygenerated among the layers of the coiled conductive foils. In FIG. 3,numerals 10, 11 and 12 designate condensers, and 7 and 8, inductances.FIG. 4 shows the appearance of the LC filter, in which a numeral 18designates a core made of ferrite or the like.

The inductances 7 and 8 in FIG. 3, are respectively formed by the coiledconductive foils 1a and 2a, and the electrostatic capacitance 12 isformed by the conductive foil 1a, the dielectric film 4, and theconductive foil 2a. Furthermore, the electrostatic capacitance 10 isformed by the conductive foils 1a and 3a and the dielectric film 4interposed between the conductive foils, and similarly, theelectrostatic capacitance 11 is formed by the conductive foils 2a and 3aand the dielectric film 4 interposed between the conductive foils.

In such an LC filter, as shown in FIG. 2, the distributed capacity 9 isformed among layers of the coil. This distributed capacity is formed inparallel with the inductances 7 and 8 as shown in FIG. 3. Since in thisembodiment, the conductive foil 3a is provided as well as the conductivefoils 1a and 2a, and the conductive foil 3a is coiled simultaneouslywith the other foils, the conductive foil 3a shields between the layersin the coil 19, and can reduce the inter-layer distributed capacity 9.FIG. 5 is a characteristic diagram showing an impedance between theterminals 20a and 21a in FIG. 3. The ordinate shows the impedance Z, andthe abscissa, the frequency f, in which f₁ is a resonance frequency incase of being devoid of the conductive foil 3a, and f₂, a resonancefrequency according to the present invention. The resonance frequency ofa circuit having a coil and a condenser can be shown by the equationf=1/2π√LC. By reducing the distributed capacity C, the resonancefrequency can be increased from f₁ to f₂, which enables the improvementof the frequency characteristic of the LC filter. Furthermore, it ispossible to enhance the effect of reducing the distributed capacity, byenlarging the width of the conductive foil 3a compared with those of theconductive foils 1a and 2a.

EMBODIMENT 2

The LC filter can be a common mode filter, by making the terminal 25a ofthe conductive foil 3a in the above Embodiment 1, a grounded terminal.

EMBODIMENT 3

FIGS. 6 through 14 are diagrams showing another embodiment of thepresent invention. FIGS. 6 and 7 show a plan and a front view of theconductive sheet, respectively. FIGS. 8, 9 and 10 are a plan, a frontview and an equivalent circuit diagram of a unit layer LC filter,respectively. FIGS. 11, 12 and 13 are a plan, a front view and anequivalent circuit diagram of a multi-layer LC filter in which the aboveunit layer LC filters are laminated by N layers, respectively. FIG. 14is a perspective view of the multi-layer LC filter in which a ferritecore is inserted.

In FIGS. 6 and 7, a notation 1a designates a ring-like conductive sheeta portion of which is cut off from an opening to a periphery thereof,20a, a terminal provided at one cut-off end of the conductive sheet, and21a, a terminal provided at the other cut-off end of the conductivesheet. A numeral 17 designates a core insertion hole. In FIGS. 8, 9 and10, a notation 2a designates a ring-like conductive sheet a portion ofwhich is cut off from an opening to a periphery thereof, similar to 1a,and has terminals 22a and 23a, similar to 1a. A numeral 4 designates aring-like dielectric film, which is sandwiched between the conductivesheets 1a and 2a, for forming a unit layer LC layer shown in theequivalent circuit of FIG. 10. In this occasion, the conductive sheets1a and 2a are shifted from each other in the circumferential directionso that the terminals 20a and 21a do not contact the terminals 22a and23a.

Next, a multi-layer LC filter is formed by laminating the unit layer LCfilters by N layers, interposing the dielectric films 4 therebetween,and connecting corresponding terminals. In FIGS. 11 and 12, a terminal21-1 of a conductive sheet 1-1 and a terminal 20-2 of a conductive sheet1-2, and the other terminal 21-2 of the conductive sheet 1-2 and aterminal 20-3 of a conductive sheet 1-3, are connected. Similarly, therespective corresponding terminals of the respective conductive sheetsare connected until a terminal 21-n-1 of a conductive sheet 1-n-1 and aterminal 20-n of a conductive sheet 1-n are connected, by which a firstmulti-layer coil-like conductive body is formed. Similarly, byconnecting conductive sheets of 2-1, 2-2, . . . , 2-n-1, and 2-n, asecond multi-step coil-like conductive body is formed. As mentionedabove, by laminating unit layer LC filters into a multi-layer body, anLC filter is obtained, in which larger values of the condenser 12, andthe inductances 7 and 8, shown in the equivalent circuit of FIG. 13, areobtained.

In this embodiment, it is not necessary to laminate and coil thesheet-like conductive foils and dielectric films, as in Embodiments 1and 2. A multi-layer body is produced by laminating the ring-likeconductive sheets and the dielectric films. Therefore, this embodimenthas an advantage in which the production of the filter is easy.

Furthermore, in this embodiment, the shape of the dielectric film isring-like. However, when the core such as a ferrite core is not used,the shape may be a disk-like one. Furthermore, the terminals forconnection, can integrally be made with the conductive sheet, orseparately made. Dielectric films or insulating films may be provided atthe top and the bottom of the filter in FIG. 12.

EMBODIMENT 4

FIGS. 15 and 16 show another embodiment of the present invention. Inthis embodiment, a multi-layer LC filter is composed of N layers of unitLC filters in which third conductive sheets are inserted between therespective unit layer LC filters of the multi-layer LC filter of theembodiment 3, interposing the dielectric films therebetween. FIG. 15 isa front view of the multi-layer LC filter, and FIG. 16 is an equivalentcircuit diagram thereof. In FIGS. 15 and 16, notations 3-1, 3-2, . . . ,3-n-1 are ring-like third conductive sheets devoid of cut-off portions,which are interposed between the respective unit layer LC filter,interposing the dielectric films 4, and which are connected to theterminal 25-n. The condensers 10 and 11 are formed by the conductivesheets 3-1, 3-2, . . . , 3-n-1. The condenser 10 is formed by the firstconductive sheets 1-2, 1-3, . . . , 1-n, the third conductive sheets3-1, 3-2, . . . , 3-n-1, and the dielectric sheets 4 interposedtherebetween. The condenser 11 is formed by the second conductive sheets2-1, 2-2, . . . , 2-n-1, the third conductive sheets 3-1, 3-2, . . . ,3-n-1, and the dielectric sheets 4 interposed therebetween.

The conductive sheets 3-1, 3-2, . . . , 3-n-1, can reduce theinter-layer distributed capacity and provide an LC filter in which thehigh frequency characteristic is improved, by shielding among therespective unit layer LC filters. The shielding effect is enhanced bymaking the size of the conductive sheets larger than those of the firstand the second conductive sheets.

Furthermore, when a core such as a ferrite core is not used, the shapeof the third conductive sheets 3-1, 3-2, . . . , 3-n-1, and thedielectric films 4 may not be a ring-like one and may be a disk-likeone. The third conductive sheets or the third conductive sheet havingdielectric films or insulating films at the outside thereof, may beprovided on the top and the bottom of the filter in FIG. 15.

EMBODIMENT 5

An LC filter can be made to a common mode filter, by making the terminal25-n of the third conductive sheets of the Embodiment 4, a groundedterminal

EMBODIMENT 6

FIG. 17 is a plan showing a laminated body wherein ring-like conductivesheet portions of which are cut off from openings to peripheriesthereof, and dielectric films are laminated. In FIG. 17, a referencenumeral 14 designates a radial line drawn from the center of the ring atthe edge of the cut-off portion. In this embodiment, a multi-layer LCfilter including N layers, of the embodiment 4 is formed, by providingthe terminals of the first and the second conductive sheets on theradial lines 14. In this embodiment, no shift is produced between theterminals, when the sheets are laminated in multi-layers, and thecorresponding terminals are connected. Therefore, the production thereofis facilitated.

Furthermore, a multi-layer LC filter having no shift, and having tightadherent characteristic, can be produced by mounting conductive sheetsand the dielectric films by an adhesive in laminating them.

The perspective view and the equivalent circuit diagram of themulti-layer LC filter of this embodiment, in which a ferrite core isinserted into the central part of the laminated rings, are the same asin FIGS. 14 and 16, respectively.

EMBODIMENT 7

In this embodiment, an integral sheet is produced, which is composed ofa dielectric film made of polyester film or polyimide film and aring-like conductive sheet with terminals as shown in FIG. 17, by usinga single-faced flexible substrate and by etching a copper foil portionthereof. By combining a plurality of the integral sheets, a multi-layerLC filter similar to embodiment 6, is produced. In this embodiment,there is an advantage of saving time in production.

EMBODIMENT 8

In this embodiment, the connection method of respective layers in themulti-layer formation of the multi-layer LC filter having thirdconductive sheets described in Embodiment 4, is changed. FIGS. 18 and 19are a plan and a front view showing the construction of the first layerof the unit layer LC filters having the third conductive sheets,respectively. FIG. 20 is a diagram showing the connection state in themulti-layer formation by using the unit layer LC filters, particularlyshowing the connection of the N-1th layer of the unit layer LC filtersand the Nth layer thereof. In FIG. 18, a reference numeral 31 designatesa cut-off portion which is cut off along the radial line from the centerof the ring-like conductive sheet 1a, 32, another cut-off portion whichis cut off along another radial line from the center of the dielectricfilm 4, which is provided at the position shifted from the portion 31 incircumferential direction by several degrees. Similarly, numerals 33,34, 35 and 36 are respectively cut-off portions provided along theradial lines from the centers of the conductive sheet 2a, the dielectricfilm 4, the conductive sheet 3a and the dielectric film 4, beingsuccessively shifted by several degrees.

In FIG. 20, a notation 21-n-1 designates a connection terminal of theconductive sheet 1-n-1, which is exposed between the cut-off portions 31and 32, of the N-1th layer of the unit LC filter, 23-n-1, a connectionterminal of the conductive sheet 2-n-1, which is exposed between thecut-off portions 33 and 34 and 25-n-1, a connection terminal of theconductive sheet 3-n-1, which is exposed between the cut-off portions 35and 36. Similarly, notations 20-n, 22-n and 24-n are connectionterminals of the conductive sheets 1-n, 2-n and 3-n of the Nth layer ofthe unit layer LC filter, respectively. By connecting these connectionterminals 21-n-1 and 20-n, 23-n-1 and 22-n, and 25-n-1 and 24-n, theconnections among the first conductive sheets, the second conductivesheets and the third conductive sheets can be made, by which theconnection between the N-1th layer and the Nth layer of the unit layerLC filter is completed. Similarly, the multi-layer LC filter having Nlayers can be obtained by connecting the unit layer LC filters from thefirst layer of the unit layer LC filter to the N-1th layer thereof inthe same way as above. The equivalent circuit in this embodiment is asshown in FIG. 16 of Embodiment 4.

According to the embodiment, the connecting positions for multi-layerformation are not exposed outside and can be accommodated inside of theouter surface of the ring-like conductive sheets. Therefore, it ispossible to downsize the LC filter.

EMBODIMENT 9

As shown in FIG. 21, in this embodiment, non-conductive ring-likemagnetic sheets are used replacing the dielectric films 4 in Embodiment4. In FIG. 21, a reference numeral 15 designates a ring-like magneticsheet. The equivalent circuit thereof is shown in FIG. 22. By insertingthese magnetic sheets, the added-magnetic-beads effect shown by thereference numerals 37 and 38 in the equivalent circuit diagram of FIG.22, can be obtained. Accordingly, as an LC filter, improvement of thefrequency characteristic, particularly, the characteristic improvementin the high frequency domain, is obtained. The condensers 10, 11 and 12in the equivalent circuit of FIG. 22 are formed by the respectiveconductive sheets and a dielectric constant of the magnetic sheettherebetween. Of course, when the capacitance of the condenser isinsufficient, the dielectric films can be added as in Embodiment 4. Forinstance, in FIG. 21, the film composition of the embodiment may be onein which the conductive sheet, the magnetic sheet, the dielectric film,the conductive sheet, . . . , are iteratively laminated.

As shown in Embodiment 6, the respective composing elements may bebonded by an adhesive agent in laminating thereof, by which shift inlaminating layers can be prevented. When the composing elements arebonded by an adhesive agent, in case that insulation between theconductive sheets and the magnetic sheets can be maintained, themagnetic sheet can be selected in wide varieties without being limitedto the non-conductive magnetic body.

Furthermore, by composing input terminals and output terminals of thefirst and the second conductive sheets, as in 20a and 21a of FIG. 17shown in Embodiment 6, the shift of connecting terminals in themulti-layer formation can be prevented. Also in case of the filter inwhich the magnetic sheets are interposed, by performing the working ofthe sheets as shown in Embodiment 8, the connecting means in themulti-layer formation in Embodiment 8 is applicable, and theminiaturization of the LC filter is made possible.

Furthermore, as shown in Embodiment 7, the use of the single-facedflexible substrate is possible.

The appearance of the multi-layer LC filter in which a ferrite core isinserted into the laminated body of the embodiment, is similar to FIG.14.

EMBODIMENT 10

In this embodiment, a multi-layer LC filter composed of N1 layers ofunit layer LC filters in Embodiment 3, is formed. On the other hand,another multi-layer LC filter composed of N2 layers of unit layer LCfilters having the third conductive sheets as in Embodiment 4, isformed. Next, a multi-layer LC filter having N1+N2 layers, is formed, byconnecting corresponding terminals of the first and the secondconductive sheets as in Embodiment 3 or in Embodiment 4, in the abovetwo filters. According to this embodiment, by selecting arbitrarily thelaminated layer numbers, N1 and N2, of the above two kinds ofmulti-layer LC filters, the values of the inductances and thecapacitances in the equivalent circuit diagram of FIG. 16, can bechanged, by which the characteristic of the LC filter can be setcomparatively easily.

A similar multi-layer LC filter can be formed by the multi-layerformation in which the connection is performed inside of the surfaces ofthe conductive sheets as shown in Embodiment 8.

EMBODIMENT 11

FIG. 23 is a plan showing an example of a conductive foil according tothe present invention, FIG. 24, a plan of a dielectric film, and FIG.25, a sectional diagram taken along the line A--A in FIG. 24 wherein theconductive sheet and the dielectric film shown in FIGS. 23 and 24, arelaminated. FIGS. 26, 29 and 32 are plans of the other conductive foils,FIGS. 27, 30 and 33, plans of the other dielectric films, and FIGS. 28,31 and 34, sectional diagrams taken along the lines A--A in FIGS. 27, 30and 33, wherein the conductive sheets and the dielectric films shown inFIGS. 26, 27, 29, 30, 32 and 33, are laminated. FIG. 35 is a connectiondiagram of the conductive sheets in FIGS. 23, 26, 29 and 32, and FIG.36, an equivalent circuit of the LC filter according to the presentinvention.

In FIGS. 23 through 36, a notation 1 designates a conductive sheet, 20a,20b, 20c, 20d, 20e, 20f, 20g and 20h, terminals, 17, a core insertionhole, 4, a dielectric film, 5a and 5b, holes for connecting theconductive sheets, 6, a protrusion for positioning, 7a and 7b,inductances, and 12, an inter-cable condenser.

In FIGS. 23, 26, 29 and 32, a notation 1 designates a conductive sheet aportion of which is cut off from an opening to a periphery thereof. Atboth cut-off edges of the conductive sheets 1, the terminals 20a, 20b,20c, 20d, 20e, 20f, 20g and 20h are integrated with the conductivefoils. The conductive sheet 1 in FIG. 23, forms a coil of 1 turn aroundthe core insertion hole 17 which is provided at the central portion ofthe dielectric film 4, from the terminal 20a to the terminal 20b.Furthermore, the terminal 20b communicates with the terminal 20c throughthe holes for connecting conductive sheets shown in FIGS. 24, 25, 27 and28, by connection thereto or by a conductive adhesive agent. Thecommunication continues to the terminal 20d, thereby forming a coil of 2turns, 7a. Similarly, the terminal 20e of the conductive sheet 1 of FIG.26, communicates with the terminal 20g of FIG. 32 around the coreinsertion hole 17, through the holes 5b for connecting conductive sheetsshown in FIGS. 27, 28, 30 and 31, at the terminal 20f, by contactthereto or by a conductive adhesive agent, and the communicationcontinues to the terminal 20h, thereby forming a coil of 2 turns, 7b. Inthis way, the respective terminals 20a, 20b, 20c, . . . are connected,and the connection diagram is as shown in FIG. 35. The inter-cablecondenser 12 is formed by the conductive sheets 1 of FIGS. 23 and 26,FIGS. 26 and 29, and FIGS. 29 and 32 and the dielectric films 4.Accordingly, the equivalent circuit of the LC filter of this inventionis as shown in FIG. 36. Furthermore, by matching the protrusions 6 forpositioning, which are installed at the dielectric films 4 of FIGS. 24,27, 30 and 33, the positioning for connecting predetermined terminalsbecomes possible.

EMBODIMENT 12

FIG. 37 is a top view of an embodiment of a two-face-substrate accordingto the present invention, FIG. 38, a bottom view of FIG. 37, and FIG.39, a sectional diagram taken along the line A--A of FIG. 37. FIGS. 40,43 and 46 are top views of the other two-face-substrates, FIGS. 41, 44and 47, bottom views thereof, and FIGS. 42, 45 and 48, sectionaldiagrams taken along the lines A--A of FIGS. 40, 43 and 46.

In FIGS. 37 through 48, a notation 1 designates a conductive sheet, 20a,20b, 20c, 20d, 20e, 20f, 20g and 20h, terminals, 17, a core insertionhole, 4, a dielectric film, 5a and 5b, holes for connecting theconductive sheets, 6, a protrusion for positioning and 13, a throughhole, inside of which is plated with a highly conductive metal such ascopper (hereinafter, through hole).

In FIGS. 37, 40, 43 and 46, a numeral 1 designates a ring-likeconductive sheets a portion of which is cut off from an opening to aperiphery thereof. On the respective cut-off ends and the otherrespective cut-off ends of these conductive sheets 1, and on the backsurfaces which are connected to the top surfaces thereof through thethrough holes 13, the terminals 20a, 20b, 20c, . . . , are provided. Theconductive sheet 1 of FIG. 37 forms a coil of 1 turn around the coreinsertion hole 17 which is provided at the central portion of thedielectric film 4 from the terminal 20a to the terminal 20b at the backsurface thereof which is connected to the other cut-off end of theconductive sheet through the through hole 13. Furthermore, the terminal20b communicates with the terminal 20c of FIG. 43 through the hole 5 forconnecting conductive sheets of FIGS. 40, 41 and 42, by contact theretoor by a conductive adhesive agent, and the communication continues tothe terminal 20d, thereby forming a coil of 2 turns. In this occasion,the thickness of the terminal 20b is larger than that of the conductivesheet 1 by those of the dielectric film 4 and the adhesive agent betweenthe conductive sheet and the dielectric film 4, as shown in FIGS. 39,42, 45 and 48. Therefore, good connection from terminal 20a to theterminal 20c is made possible. Similarly, the terminal 20e of theconductive sheet 1 in FIG. 40 communicates with the terminal 20g of FIG.46 around the core insertion hole 17 through the through hole 13, whichis connected to the terminal 20f of the back surface, of which thicknessis controlled as in the terminal 20b, through the hole 5 for connectingconductive sheets shown in FIGS. 43, 44 and 45, by contact thereto or bya conductive adhesive agent, and the communication continues to theterminal 20h of FIG. 47 which is connected to the back surface thereofthrough the through hole 13, thereby forming a coil of 2 turns. In thisway, the respective terminals 20a, 20b, 20c, . . . , are connected, andthe connection diagram is as shown in FIG. 35, as in Embodiment 11.Furthermore, an inter-cable condenser is formed by the conductive sheets1 in FIGS. 37 and 40, FIGS. 40 and 43, and FIGS. 43 and 46 and thedielectric films 4. Accordingly, the equivalent circuit of this LCfilter of the present invention is as shown in FIG. 36, as in Embodiment11. Furthermore, by matching the protrusions 6 for positioning which areinstalled in the dielectric films 4 in FIGS. 37, 40, 43 and 46, thepositioning for connecting predetermined terminals, is made possible.Furthermore, in this embodiment, the shape of the conductive sheet isdetermined as ring-like. However, it is not necessary to restrict theperipheral shape to circle. This is also applicable to the followingembodiments.

EMBODIMENT 13

FIG. 49 is an exploded view of an embodiment of a multi-layer substrateof the present invention. In FIG. 49, notations 1a, 1b, 1c and 1ddesignate respectively conductive sheets of the first, the second, thethird and the fourth layers, 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h,20i, 20j and 20k, terminals, 17, a core insertion hole, 4a, 4b, 4c and4d, respectively dielectric films of the first, the second, the thirdand the fourth layer, 6, a protrusion for positioning, and 13, a throughhole.

In FIG. 49, a notation 1 designates a ring-like conductive sheet aportion of which is cut off from an opening to a periphery thereof.Terminals 20a, 20b, . . . , are provided at both cut-off ends of theconductive sheets 1. The conductive sheet 1a of FIG. 49 forms a coil of1 turn by communicating the terminal 20a to the terminal 20b at theother cut-off end, around the core insertion hole 17. The terminal 20bis communicated with the terminal 20c of the conductive sheet 1 of thethird layer through the through holes 13, and the communicationcontinues to the terminal 22d of the same layer thereby forming a coilof 2 turns, and to the terminal 20i again through the through holes 13.Furthermore, the terminal 20j of the first layer communicates with theterminal 20e provided at the conductive sheet 1b of the second layerthrough the through hole 13, and to the terminal 20k through theterminals 20f, 20g, and 20h, thereby forming a coil of 2 turns. Theconductive sheets 1 of the first layer and the second layer, the secondlayer and the third layer, the third layer and the fourth layer composean inter-cable condenser by interposing the dielectric films 4.Accordingly, the equivalent circuit for this embodiment is as shown inFIG. 36, as in Embodiment 11. By connecting the multi-layer substratesin one step or in multiple steps, the LC filter is composed. In thisoccasion, the protrusions 6 for positioning which are provided at thedielectric films 4, are matched, and terminal 20i of a multi-layersubstrate is connected to the terminal 20a of the other multi-layersubstrate, and the terminal 20k communicates with the terminal 20j ofthe other mulit-layer substrate by contact thereto or by a conductiveadhesive agent.

EMBODIMENT 14

FIG. 50 is a top view of an embodiment of a two-face-substrate accordingto the present invention, FIG. 51, a bottom view of FIG. 50, and FIG.52, a sectional diagram taken along the line A--A of FIG. 50. FIG. 53 isa top view of anther two-face-substrate, FIG. 54, a bottom view thereof,and FIG. 55, a sectional diagram taken along the line A--A of FIG. 53.Furthermore, FIG. 56 is a connection diagram of conductive sheetsbetween those in FIG. 50 and those in FIG. 53, and FIG. 57, anequivalent circuit of an LC filter of the present invention.

In FIGS. 50 through 57, a notation 1 designates a conductive sheet, 20l,20m, 20n and 20p, terminals, 17, a core insertion hole, 4, a dielectricfilm, 5, a hole for connecting the conductive sheets, 6, a protrusionfor positioning, 12, an inter-cable condenser, and 13, a through hole.

In FIGS. 50 and 53, a numeral 1 designates a ring-like conductive sheeta portion of which is cut off from an opening to a periphery thereof.Terminals 20m, 20l, 20n and 20p are provided at both cut-off ends of theconductive sheets 1 and the back surfaces connected by the through holes13. A plurality of two-face-substrates of FIG. 50 are provided, and twoof the terminals 20l and two of the terminals 20m of FIG. 51 areconnected by contact thereto or by a conductive adhesive agent, that is,a plurality of conductive sheets 1 are connected in parallel. Similarly,a plurality of two-face-substrates of FIG. 53 are provided, and two ofthe terminals 20n and two of the terminals 20p of FIG. 54 are connectedby contact thereto or by a conductive adhesive agent. In thisconnection, by matching the protrusions 6 for positioning which areattached to the dielectric films 4 shown in FIGS. 50, 51, 53 and 54, thepositioning for connecting predetermined terminals is made possible. Thethickness of the terminals 20l and 20p is larger than that of conductivesheet 1 by those of the dielectric film 4 and the adhesive between theconductive sheet and the dielectric film 4. Therefore, good connectionis made possible among these terminals. By alternatively laminating, twopairs of conductive sheets 1 which are parallely connected as above, asin the connection diagram of FIG. 56, an inter-cable condenser 12 iscomposed as shown in FIG. 57. In this construction, the protrusions 6for positioning are utilized for positioning the substrates as in theconnection between each of the same two-face-substrates, and a terminalof a substrate is connected to another terminal, which is provided atanother substrate and of which thickness is controlled, through the hole5 for connecting conductive sheets.

EMBODIMENT 15

FIG. 58 is a top view of an embodiment of a two-face-substrate of thepresent invention, FIG. 59, a bottom view of FIG. 58, FIGS. 60, 61 and62, sectional diagrams taken along the line A--A, the line B--B, and theline C--C of FIG. 58, respectively. FIGS. 63, 68, 73, 78, 83, 88 and 93are top views of the other two-face-substrates, FIGS. 64, 69, 74, 79,84, 89 and 94, bottom views thereof, FIGS. 65 through 67, FIGS. 70through 72, FIGS. 75 through 77, FIGS. 80 through 82, FIGS. 85 through87, FIGS. 90 through 92, and FIGS. 95 through 97, sectional diagramstaken along respectively the lines A--A, the lines B--B, and the linesC--C of FIGS. 63, 68, 73, 78, 83, 88 and 93. FIG. 98 is a connectiondiagram of the conductive sheets of the two-face-substrates, and FIG.99, an equivalent circuit of the LC filter of this invention.

In FIGS. 58 through 99, notations 1a and 1b designate conductive sheets,20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20q, 20r, 20s, 20t, 20u,20v and 20w, terminals, 17, a core insertion hole, 4, a dielectric film,5a, 5b and 5c, holes for connecting conductive sheets, 6, a protrusionfor positioning, 7a and 7b, inductances, 13, a through hole and 10 and11, cable-to-earth condensers.

In FIGS. 58, 68, 78 and 88, a notation 1a designates a conductive sheeta portion of which is cut off from an opening to a periphery thereof.Terminals 20b, 20i, 20u, 20f, 20d, 20v, 20w and 20h are provided on backsurfaces connected to ones and another ones of cut-off edges through thethrough holes 13. The conductive sheet 1a of FIG. 58 forms a coil of 1turn by communicating the terminal 20a with the terminal 20b on the backsurface which is connected to the other cut-off end through the throughhole 13, around the core insertion hole 17 provided at the central partof the dielectric film 4. Furthermore, the terminal 20b communicateswith the terminal 20u of FIG. 68 through the hole 5a for connectingconductive sheets of FIGS. 63, 64 and 65, by contact thereto or by aconductive adhesive agent, and the communication continues by passingthrough the hole 5a for connecting conductive sheets of FIGS. 73 through75, to the terminal 2Ob by contact thereto or by a conductive adhesiveagent, thereby forming a coil 7a of 2 turns. Furthermore, thecommunication continues to the terminal 20w of FIG. 88 passing throughthe hole 5a for connecting conductive sheets of FIGS. 83 through 85. Thethicknesses of the terminals 20b, 20u, 20 d and 20w are larger thanthose of the conductive sheets 1a by the thickness of the conductivefilm 4 and an adhesive agent between the conductive sheet and thedielectric film 4, as shown in FIGS. 60, 70, 80 and 90. Therefore, goodconnection is made possible among terminals. Similarly, the conductivesheet 1a of FIG. 68 forms a coil of 1 turn by communicating the terminal20i of FIG. 58 with the terminal 20e through the hole 5b for connectingconductive sheets of FIGS. 63, 64 and 66, by contact thereto or by aconductive adhesive agent, and by the communication continuing to theterminal 20f of the back surface which is connected to the other cut-offend through the through hole 13. Furthermore, the terminal 20fcommunicates with the terminal 20v of FIG. 78 through the hole 5b forconnecting conductive sheets of FIGS. 73, 74 and 76, and by contactthereto or by a conductive adhesive agent, and by the communicationcontinuing to the terminal 20g of FIG. 88 through the hole 5b forconnecting conductive sheets of FIGS. 83, 84 and 86, and to the terminal20h, thereby forming the coil 7b of 2 turns. The thicknesses of theterminals 20i, 20f, 20v and 20h are larger than that of the conductivesheet 1a, by the thickness of the dielectric film 4 and an adhesiveagent between the conductive sheet and the dielectric film 4, as shownin FIGS. 61, 71, 81 and 91. Therefore, good connection is made possibleamong respective terminals.

In the conductive sheet 1b of FIG. 63, the terminal 20q is provided atthe through hole 13, which communicates with the terminal 20r throughthe hole 5c for connecting conductive sheets of FIGS. 68, 69 and 72, bycontact thereto or by conductive adhesive agent, and the communicationcontinues to the terminal 20s of FIG. 83 through the hole 5c forconnecting conductive sheets of FIGS. 78, 79 and 82, by contact theretoor by a conductive adhesive agent, and to the terminal 20t of FIG. 93through the hole 5c for connecting conductive sheets of FIGS. 88, 89 and92, by contact thereto or by a conductive adhesive agent, and finally tothe ground.

In this way, the respective terminals are connected and the wiringdiagram is as shown in FIG. 98. Cable-to-earth condensers 10 and 11 arecomposed by conductive sheets 1 between FIGS. 58 and 63, FIGS. 63 and68, FIGS. 68 and 73, FIGS. 73 and 78, FIGS. 78 and 83, FIGS. 83 and 88,and FIGS. 88 and 93 and the dielectric films 4. Accordingly, theequivalent circuit of this LC filter is as shown in FIG. 99.

Furthermore, by matching the protrusions 6 for positioning which areinstalled at the dielectric films 4 for the respectivetwo-face-substrates, the positioning for connecting predeterminedterminals is made possible.

A new LC filter is composed by performing a single step or a multi-stepconnection of the LC filters composed as above, in series, and byconnecting thereto in series the respective filters in Embodiment 12 andEmbodiment 14. In this filter, the respective constants of the LC filtercan be set independently by controlling number of conductive sheetswhich are laminated in multi-steps in the respective filters, of thefirst filter wherein the conductive sheets for inductances and forinter-cable condensers, are connected in series, the second filterwherein the conductive sheets for the cable-to-earth condenser areconnected in parallel, and the third filter wherein the other conductivesheets and the dielectric sheets are inserted between the respectiveconductive sheets for the cable-to-earth condenser and the inductances,and the inserted conductive sheets are earthed. FIG. 100 is anequivalent circuit diagram of such an LC filter.

Since this invention is composed as explained as above, the inventionhas the following effects.

Since this LC filter is made by the coiling method or by the laminatingmethod, provided with the third conductive sheets, as well as the firstand the second conductive sheets, the third conductive sheets shield thefirst and the second conductive sheet layers, the distributedcapacitance is reduced, the resonance frequency of the coil isincreased, and the high frequency characteristic of the LC filter isimproved.

Furthermore, as for the laminating type LC filter, the magnetic sheetsinserted between the conductive sheets, have an effect similar to theadded-magnetic-beads effect, and similarly improve the high frequencycharacteristic.

Furthermore, in the LC filter made by laminating the ring-likeconductive sheets a portion of each of which is cut off from an openingto a periphery thereof and the dielectric films, the coiling operationof the conductive sheets and the dielectric films is not necessary,which facilitates the production of the LC filter.

Furthermore, the LC filter of a target characteristic can easily beobtained by connecting two kinds of filters having different unitcompositions of inductances and capacitances in arbitrary numbersrespectively, and by combining these two multi-layer LC filters.

Furthermore, the LC filter is realized by laminating the conductivesheets which form inductance and capacitance, in multi-layers, whereinit is not necessary to take out the terminals, the automation of theproduction is enabled, and the production cost is reduced.

Furthermore, in case of the two-face-substrate, good connection isenabled even in case of connecting the conductive sheets in multi-steps,by increasing the thickness of the terminal on the back surface thereoflarger than the terminal thickness of the top surface by the thicknessof the dielectric film layer.

The promotion of the characteristic of the filter is made possible sincethe inductance and the capacitance can independently be set.

We claim:
 1. An LC filter which comprises:at least two conductive sheetseach having a first opening provided at a central portion of theconductive sheet, cut-off portions provided from the first opening to aperiphery of each of the conductive sheets, each of said conductivesheets including first and second terminals consisting of first andsecond projections disposed in the same plane and formed by said cut-offportion; and at least one dielectric film having a second opening with awidth substantially equal to the width of said terminals of saidconductive sheets, for connecting the conductive sheets situated aboveand below said dielectric film.